Twist drill grinding machine



Nov. 1, 1932.

v. JERECZEK 1,886,025

TWIST DRILL GRINDING MACHINE Filed Aug. 9. 1930 3 Sheets-Sheet 1 6 75 2! lnvenfon: V77: tor Jreczek Nov. 1, 1932. v, JERECZEK 1,886,025

TWIST DRILL GRINDING MACHINE- Filed Aug. 9. 1930 s Sheets-Sheet 2 A M I W wzw f M gig s.

Nov. 1, ,1 932.

v. JERECZEK 1,886,025 TWIST DRILL GRINDING MACHINE Filed Aug, 9. 1930 3 Sheets-Sheet 3 V/A'for Jrecze/ Patented Nov. 1, 1932 PATENT OFFICE VIKTOR JERECZEK, OF BERLIN-STEGLITZ, GERMANY TWIST DRILL GRINDING MACHINE Application filed August 9, 1930, Serial No.

This invention relates to a machine for grinding grooves consisting of non-uniform profiles in surfaces of twist and other drills.

The invention differs from known ma- 5 chines employed for this purpose in that a sharp-edged, preferably truncated coneshaped grinding disc is employed for grinding the grooves and in that the grinding disc together with its spindle is so adjustably ar- 10 ranged with respect to the work feed slide at any desired inclination thereto that the nonuniform parts of the groove profiles corresponding to this shape and position of the I grinding disc merge. without a break into one 15 another. The path of the work feed slide follows the direction of the grooves.

This method 0f grinding is known per se for the production of grooves in other objects, but in this case however it is principal- 20 ly a question of circular profiles in ball hearing races and so forth which involves a corresponding circular feed.

In contradistinction thereto the present in vention is concerned with sharpening drills which does not involve circular feeding motions, but only a straight to and fro motion. Further, the profile which is ground is not uniform, but becomes .shallower gradually rearwardly.

All this plays no part in the known application of such grinding.

Reference will now be made to the accompanying drawings illustrating one constructional form according to the invention.

Fig. 1 is a side elevation of the new machine viewed from the operators side.

Fig. 2 is a part sectional front elevation.

Fig. 3 is a plan view of the gripping de-' vice, the rear counter bearing of the drill and its retaining device being shown swung through an angle of 90.

Fig. 4 is a partial plan view of Fig. 1. Fig. 5 is a front elevation similar to Fig. 2 the grinding disc trimming or truing device being shown in section.

Fig. 6 is a part sectional and front elevation of the trimming mechanism.

Fig. 7 is a side elevation corresponding to Fig. 6. v

Fig. 8 is an enlarged partial front eleva- 474,227, and in Germany August 27, 1929.

erating parts and the grinding wheel.

A grinding disc support 3 is mounted on transverse guides on the machine frame 1 so as to be capable of 'reciprocatory movement. A housing 4 is mounted on the support and carries the grinding spindle 5 and grinding disc 6 and at thesame time may form the housing of an electric motor by whichthe spindle 5 and'the grinding disc 6 mounted thereon can be rotated. It is to be understood that any other suitable or known means, for example, pulley drive, may be employed for driving the grinding disc. The housing 4 is rotatably supported through the medium of a pin 7 disposed perpendicularly to the path of movement of the reciprocatory support so that the axis of the grinding spindle 5 and grinding disc 6 may be set at an inclination relatively to the direction of movement of the said support.

The reciprocatorymovement of the support 3 longitudinally of the guides 2 is effected in the example illustrated in the drawings, by hand, viz, by means of a toothed rack 8 engaging a toothed quadrant 9. This quadrant is mounted on a stationary pin 10 and may be swung angularly by a hand lever 11.

According to the invention the grinding disc 6 mounted on the spindle 5 is shaped like a truncated cone, i. c. it has plane disc surfaces and a convex surface, which constitutes the grinding surface proper of the discfand runs between the two end faces with a rectilineal generatrix so that it merges into them forming sharp angles. The grinding is essentially effected by the angular portions.

A vertically adjustable bracket or table 12 is supported on the frame 1. The vertical adjustment is effected by a hand wheel 13 and a screwed spindle 14. The table is held in position by a clamp 15. A plate 16 is supported on the table 12 so as to be capable of adjustment perpendicularly .to the movement of the reciprocatory grinding disc; The adjustment is effected by a regulating wheel 17 The gripping device for the twist drill to be intermediate rod or by other means.

sharpened is mounted on the plate 16 preferably by means of an intermediate rotary piate. This gripping device is provided with two clamping blocks 18 and 19 which can be moved to and fro through an angle determined by the shape of the twist drill, and preferably also adjustable. The two blocks 18 and 19 are provided with cut out portions in their ends directed towards each other, these portions being accurately grooved cor responding to the so-called phase ofthe twist drill to be sharpened. These cut out portions therefore enable the blocks to grip opposed points of the spiral. An abutment 2O accurately adjustable in the axial direction of the drill is provided near the two blocks 18 and 19. When the point of the drill rests against the abutment the main cutting edge to he sharpened is so adjusted that it is parallel or substantially parallel to the direction of motion of the reciprocatory grinding disc and is adjusted horizontally. As the twist drill is able to move to a certain extent similar to a nut inthe two blocks 18 and 19 it is ossible without diiiiculty upon suitable adustment of the abutment 20 to ensure auto 'matically correctadjnstment of the main cutting edge to be sharpened.

On theside of the plate 16 remote from the abutment 20 a regulating collar 22 is non-rotatably mounted on an arm 21 on which however it can be reciprocated. The collar is provided with a dead centre 23 restin against the shank end of the drill.

The two blocks 18 and 19 are pivoted by members 24 and 25 to a common operating lever 26 which is rigidly secured on a verticalpin 27. The pin isrotatably supported in a lateral housing 28 of the plate 16 and is provided at its lower end with a quick pitch screw-threaded spindle 29. The internal screw thread of a sleeve 30 engages the screwthreaded part of the spindle. The sleeve is longitudinaily movable but non-rotatahly sup rted in the housing 28 and is mounted on t 0 upper end of a spindie 31, The spindle 31 is constantly under the action of a compression spring 32 which tends to hold the spindle and its screw-threaded sleeve 30 permanently in the upper position with respect to the screw-threaded spindle 29 in which the blocks 18 and 19 occupy their engaging positions.

hen the spindle 31 is moved downwards against the action of the spring 32 the'screwthreaded spindle 29 is rotated and the lever 26 is rocked so that the gripping device is released and a drill may be placed in position or removed. The downward movement of the spindle maybe effected by a pedal and an The trimming-device by means of which the truncated shape of the grinding disc may be reconditioned and by which the trimming oi the disc to any desired length of convex surface is facilitated is mounted on an arm 33 which can be rocked about a lateral pin 34 of the cross plate 16 and set in an adjuster position by means of a clamp 35. A sleeve 36 is mounted in the-eye of a lever 33 and may be swung about its axis. The sleeve 36 can be held by a clamp 37 in an inclined position which corresponds to the convex surface angle of the grinding disc to be trimmed. A

shaft 38 is rotatably supported in the sleeve 36 and may be rotated by means of a hand wheel 39 secured to one end of the shaft. The other end of the shaft carries a head 41 provided with a plain screw-thread i). A transverse slide 42 engages with the screw-thread 40 which rotates in a housing formed by an enlargement of the sleeve 36. The slide 42 is guided by a transverse groove of this housing and is provided at its upper end with a trimming diamond 43. By rotation of the screw-threaded head 41 h means of hand wheel 39 the trimming diamond is moved longitudinaliy of the convex surface of the grinding disc through an angle which is de termined by the inclined position of the housing sleeve 36. When the clamp 35 is released the entire trimming device may be lowered laterally.

When the machine is in operation, the reciprocation of the rotating grinding disc in the direction ofthe pitch of the spiral of the drill does not result in an undesired sharp edged out being made in t e drill in spite of the sharp edge of the grinding disc as the disc is not arranged parallel to the direction of its reciprocation butat an angle thereto. By adjusting this angle the profile to be ground by the .disc can be varied.

What I claim is: p

1. A twist drill grinding machine comprising in combination a grinding disc of truncated cone form having sharply formed convex surface angles, a reeiprocatory supportfor said grinding disc and means for setting said grinding disc axis at an inclination relatively to the direction of movement of said reciprocatory support, a work carrier for non-rotatably holding the work piece, and means .for rotating said grinding disc.

2. A twist drill grindin machlne comprising in combination a grin ing disc for grinding the main cutting edge of the tool, said grinding disc being of truncated cone form associated with said engaging surfaces whereby the main cutting edge of said tool to be sharpened is set automatically in the direction of movement of said reciprocatory support when the point of the tool comes against said abutment.

3. A twist drill grinding machine comprising in combination a grinding disc for grinding the main cutting edge of the tool, said grinding disc being of truncated cone form and having sharply formed convex surface angles, means for rotating said grinding disc, :1 reciprocatory support for said grinding disc, means for setting said grinding disc axis at an inclination relatively to the direction of movement of said reciprocatory support, a movable tool support, a gripping device for the tool comprising 'a pair of gripping members having opposing surfaces shaped to correspond to the tool groove with which they engage and means including a common operating element connecting said members for enabling them to be moved to and fro relatively to each other through an adjustable angle, and an abutment for said tool associated with said engaging surfaces whereby the main cutting edge of said tool tobe sharpened is set automatically in the direction of movement of said reciprocatory support when the point of the tool comes against said abutment.

at. A twist drill grinding machine comprising in combination a grinding disc for grimling the main cutting edge of the tool, said grinding disc being of truncated cone form and having sharply formed convex surface angles, means for rotating said grinding disc, a reciprocatory support for said grinding disc, means for setting said grinding disc axis at an inclination relatively to the direction of movement of said reciprocatory support, a movable tool support, a gripping device for the tool comprising a pair of gripping members having opposing surfaces shaped to correspond to the tool groove with which they engage and means including a common operating element connecting said members for enabling them to be moved to and fro relatively to each other, through an adjustable angle, an abutment for said tool associated with said engaging surfaces wh ereby the main cutting edge of said tool to be sharpened is set automatically in the direction of movement of said reciprocatory support when the point of the tool comes against said abutment,and an adj ust-able dead centre for axially supporting said tool.

5. A twist drill grinding machine comprising in combination a grinding disc for grinding the main cutting edge of the tool, said grinding disc being of truncated cone form and having sharply formed-convex surface angles, means for rotating said grinding disc, a reciprocatory support for said grind ing disc, means for setting said grinding disc axis at an inclination relatively to the direction of movement of said reciprocatory support, a movable tool support, a gripping device for the tool comprising a pair of gripping members having opposed surfaces shaped to correspond to the tool groove with which they engage and means for moving said gripping members relatively to each other including a common operating element connecting them together, pedal operated control gear and resilient means tending to hold the members in their gripping positions, an abutment for said tool associated with said engaging surfaces whereby the main cutting edge of said tool to be sharpened is set automatically in the direction of movement of .said reciprocatory support when the point of the tool comes against said abutment, and an adjustable dead centre for axially supporting said tool.

6. A twist drill rinding machine c0mprising in combination a grinding disc for grinding the main cutting edge of the tool, said grinding disc being of truncated cone form and having sharply formed convex surface angles, means for rotating said grinding disc, a reciprocatory support for said rinding disc, means for setting said grinding disc axis at an inclination relatively to the direction of movement of said reciprocatory support, a movable tool support, a gripping device for the tool comprising a pair of gripping members movable angularly relatively to each other and having opposing surfaces shaped to correspond to the tool groove with which they engage and an abutment for said tool associated with said engaging surfaces whereby the main cutting edge of said tool to be sharpened is set automatically in the direction of movement of said reciprocatory support when the point of the tool comes against said abutment.

7. A twist drill grinding machine comprising a grinding disc, a support therefor, means for rotating said grinding disc, a work carrier for non-rotatably holding the Work piece, and a gripping device for engaging said work comprising a pair of angularly movable gripping members, a rocking mem ber connected to each of said gripping mem bers, a'pivot pin fixed to said rocking member, a screw-threaded extension on said pin, an internally screw-threaded sleeve engaging the screw thread portion of said pin, a spring acting on said sleeve tending to hold said "members in gripping engagement with the work, and pedal operating gear connected to an extension of said sleeve.

In testimony whereof I afiix my signature.

VIKTOR J ERECZEK. 

